The goal of this project is to develop a small, easily inserted, intraesophageal probe containing three pH sensors, two pressure transducers, and a single liquid infusion channel. This probe will be low-cost and durable, safety and easily tolerated by most patients for up to 48 hours in the home and work environment. It will interface with a small (portable) auto-infusion device and a portable, programmable microcomputer with multiple sensor inputs (including a patient event marker), capable of recording continously for more than one week on a single battery charge. The proposed system would be useful for the evaluation and management of gastroesophageal reflux and esophagitis, abnormal esophageal motility, obscure chest pain, pulmonary disease caused by silent esophageal reflux, sudden infant death syndrome, and obscure nocturnal attacks. A subsequent Phase II proposal would be directed towards clinical testing, validation, and design iterations. The proposal is innovative in bringing together new sensor technology, low-cost fabrication techniques, solid-state portable monitors and auto-infusion devices. The potential for commercial success is indicated by the following: significant medical need, low cost of the device and of the actual clinical procedure, and a system which is designed for patient acceptance.